The objectives of this study are: 1) to discover whether micropulses of ACTH can be identified in the peripheral plasma of humans; 2) to investigate whether the amplitude, frequency, pulse duration and interpulse interval of ACTH micropulses change with age; 3) to investigate whether these parameters are altered in major depression; and 4) to correlate changes in pulsatile ACTH secretion with results of dexamethasone suppression test and twenty-four hour urinary free cortisol.